In view of high luminance (high luminous intensity) and low power consumptions, various lighting packages having LED devices (light-emitting diodes hereinafter simply called LEDs) as light-emitting devices have been introduced commercially. Lighting packages incorporating LEDs ranging from lighting fixtures built up of a mounting vessel (lighting vessel) and one or more LEDs mounted on it and designed with relatively low luminous intensity for indoor lighting to upsized floodlights used for night floodlighting at construction sites and floodlighting used in public installations and sports arenas are or being reduced down to practice in large quantities of light and packages shapes and sizes.
Referring to LED floodlights that must emit out a larger quantity of light as compared with indoor lighting equipments, there are mounting demands for not only lightweight, transportable and relatively small ones but also outdoor floodlights that are less costly and can be temporarily or fixedly mounted in easily installable, outdoor sports arenas. In an LED floodlight package used for such floodlights, the number of LED devices mounted per LED floodlight is greater as compared with LED lighting fixtures or the like used indoors, and for a parallel arrangement of plural such floodlights, it is required to provide a mechanism for efficient radiation of heat generated from them.
Some lighting packages having a radiation fin or other heat sink on an LED-mounted substrate are available; however, it is still difficult to obtain sufficient heat radiation effects. This difficulty may possibly be eliminated by the provision of a forced cooling fan or a liquid circulation cooling structure; however, additional costs will not only be necessary, but there will be a hindrance to wide use as well. Further, when a power circuit is incorporated in it, it is also required to dispose heat generated from it.
Referring to prior arts concerning the LEDs in such LED floodlights, the structure for disposing (dissipating) heats generated from power circuits and LED modules are disclosed typically in Patent Publications 1, 2, 3, 4, 5 and 6.
Patent Publication 1 discloses a LED lighting apparatus in which a LED unit having a plurality of LED devices is mounted on the surface of an aluminum metal unit having a heat radiation fin on the back, and an power supply is fixed on the heat radiation fin thereby thermally isolating off the aluminum metal unit so that the heat of the LED unit is dissipated without being hampered by the heat of the power supply.
Patent Publication 3 discloses that a substantially rectangular cooler apparatus formed of an aluminum member is used, and a mounting substrate having LEDs on its bottom surface is mounted on the bottom surface thereof. The cooler apparatus is provided with an airflow passage communicating from its side surface to its top surface, and air within the airflow passage is warmed by heat generated as the LEDs are held on, exiting out from an upper opening in the form of an ascending current. This airflow sucks in surrounding cold air via a side opening and a similar ascending airflow is created accordingly so that heat generated as the LEDs are held on can be dissipated.
In the lighting apparatus disclosed in Patent Publication 3, a heat radiator is mounted on the back surface of the main unit, and a cooling fan and airflow are attached to the heat radiator so that the heat radiation effect on LEDs by the cooling fan is improved.
Among large quantity-of-light LED floodlights in particular, there is for instance a fish-luring light disclosed in Patent Publication 4.
In this fish-luring light, a thick clad of copper foils is interposed between an insulating flat plate having a number of LEDs mounted on it and a heat sink for efficient transmission of generated heat to the fin and dissipation.
Patent Publication 5 discloses a large quantity-of-light assembly wherein a multiplicity of LEDs are mounted on a substrate, and the LEDs are forcedly cooled by a heat pipe attached to the back side of the substrate in which pipe there is a circulation of a working fluid (methyl alcohol or the like) having infrared ray-emitting powders mixed with it, and Patent Publication 6 discloses a large quantity-of-light LED module of small size in which plural LED dies are mounted on a circuit board via a bear chip process.